1. Field of the Invention
The present invention relates to a novel anaerobic adhesive composition which cures rapidly that can be useful for curable compositions, such as adhesives and sealants.
2. Brief Description of Related Technology
Anaerobic adhesive compositions generally are well-known. See e.g. R. D. Rich, “Anaerobic Adhesives” in Handbook of Adhesive Technology, 29, 467-79, A. Pizzi and K. L. Mittal, eds., Marcel Dekker, Inc., New York (1994), and references cited therein. Their uses are legion and new applications continue to be developed.
Conventional anaerobic adhesives ordinarily include a free-radically polymerizable acrylate ester monomer, together with a peroxy initiator and an inhibitor component. Often, such anaerobic adhesive compositions also contain accelerator components to increase the speed with which the composition cures.
Ferrocene-based anaerobics are known to liberate active iron under acidic conditions. This promotes cure on low-activity surfaces. Malofsky in U.S. Pat. No. 3,855,040 described a novel anaerobic formulation capable of curing on surfaces with low activity toward anaerobic cure, activated by strong acids such a methanesulfonic acid. The strong acid primer liberates active iron from the ferrocene which will react with the cumene hyperoxide, liberating free radicals suitable for polymerization of the acrylic monomers. The use if such acids can be undesirable because of their nature.
Non-ferrocene activated systems are also well known. For example, certain LOCTITE-brand anaerobic adhesive products available from Henkel Corporation use either saccharin alone or both saccharin and acetyl phenylhydrazine (APH) in various anaerobic adhesives.
U.S. Pat. No. 6,835,762 (Klemarczyk) provides an anaerobic curable composition based on a (meth)acrylate component with an anaerobic cure-inducing composition substantially free of acetyl phenylhydrazine and maleic acid and an anaerobic cure accelerator compound having the linkage —C(═O)—NH—NH— and an organic acid group on the same molecule, provided the anaerobic cure accelerator compound excludes 1-(2-carboxyacryloyl)-2-phenylhydrazine.
U.S. Pat. No. 6,897,277 (Klemarczyk) provides an anaerobic curable composition based on a (meth)acrylate component with an anaerobic cure-inducing composition substantially free of saccharin.
U.S. Pat. No. 6,958,368 (Messana) provides an anaerobic curable composition. This composition is based on a (meth)acrylate component with an anaerobic cure-inducing composition substantially free of saccharin.
Notwithstanding the state of the art, there is an on-going desire to find alternative technologies for anaerobic compositions to differentiate existing products and provide supply assurances in the event of shortages or cessation of supply of raw materials. Moreover, since certain of the raw materials used in anaerobic cure inducing compositions have to one degree or another come under regulatory scrutiny, alternative components would be desirable. There is a need to avoid using such compounds in view of the corrosivity and handling problems involved. Accordingly, it would be desirable to identify new materials that function in anaerobically curable compositions.